`Fe(OH)_(2)` is precipitated from Fe(II) solutions as a while solid turns dark green and then brown due to the formation of:

Options

A. `Fe(OH)_(2) and Fe(OH)_(3)`
B. Only `Fe(OH)_(3)`
C. `Fe_(2)O_(3)*(H_(2)O)_(n)`
D. `Fe_(2)O_(3)*2H_(2)O`

Answer

To solve the question regarding the precipitation of `Fe(OH)₂` from Fe(II) solutions and the color changes observed, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Initial Precipitate**:
- When `Fe(II)` ions (ferrous ions) react with hydroxide ions, they form `Fe(OH)₂`, which is a white solid.
- The reaction can be represented as:
\[ \text{Fe}^{2+} + 2 \text{OH}^- \rightarrow \text{Fe(OH)}_2 \text{ (s)} \]

2. **Observation of Color Change**:
- The white solid `Fe(OH)₂` does not remain white for long. It undergoes changes in color, first turning dark green and then brown.
- This color change indicates a transformation in the oxidation state of iron.

3. **Formation of Ferric Hydroxide**:
- Upon exposure to air (oxygen), `Fe(OH)₂` can oxidize to `Fe(III)`, forming `Fe(OH)₃`, which is typically a brown solid.
- The reaction can be represented as:
\[ 4 \text{Fe(OH)}_2 + O_2 + 2 \text{H}_2O \rightarrow 4 \text{Fe(OH)}_3 \]

4. **Identifying the Intermediate**:
- The dark green color observed can be attributed to the formation of a mixed hydroxide or an intermediate compound before it fully oxidizes to `Fe(OH)₃`.
- The dark green color is often associated with the presence of `Fe(II)` and `Fe(III)` in the solution.

5. **Final Product**:
- Eventually, `Fe(OH)₃` can dehydrate to form `Fe₂O₃·nH₂O`, which is the brown solid observed.
- The final reaction can be represented as:
\[ 2 \text{Fe(OH)}_3 \rightarrow \text{Fe}_2\text{O}_3 \cdot 3 \text{H}_2\text{O} \]

6. **Conclusion**:
- The color change from white to dark green and then to brown is due to the formation of `Fe(OH)₃` (ferric hydroxide) and its subsequent dehydration to `Fe₂O₃·nH₂O`.

### Final Answer:
The formation of `Fe(OH)₃` (ferric hydroxide) from `Fe(OH)₂` is responsible for the observed color changes.